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Intro to Audiology > 1 - Anatomy & Physiology of Inner Ear > Flashcards

1 - Anatomy & Physiology of Inner Ear Flashcards

0
Q

What do we call the canals that house the inner ear?

A

The labyrinth

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1
Q

Where is the part of the ear that is not visible embedded?

A

The temporal bone

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2
Q

What are the three parts of the inner ear?

A

Semicircular canals

Vestibule

Cochlea

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3
Q

Impedence

A

The sum of all energy that opposes the transmission of sound

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4
Q

What happens if the impedance of two mediums is unequal?

A

It is not possible to easily transmit sound from one to the other

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5
Q

What creates the impedance balance of the inner ear? What does this require?

A

The inner ear fluids create the impedance imbalance

This means more energy is required to produce a sound wave

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6
Q

What is the function of the cochlea?

A

To transduce mechanical energy into electrical or neural energy

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7
Q

What two things does the oval window connect?

A

The stapes to the cochlea

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8
Q

What is the cochlea’s inner wall called?

A

The modiolus

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9
Q

What is the name of the small bony shelf that protrudes from the modiolus?

A

Spiral Lamina

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10
Q

Where is perilymph found?

A

In the scala vestibuli and the scala tympani

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11
Q

What is the name for the small opening at the apical end of the cochlea?

A

Helicotrema

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12
Q

The oval window transmits vibration into the ___________.

A

Scala vestibuli

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13
Q

The round window terminates the __________.

A

Scala tympani

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14
Q

What is the triangular sac of fluid that runs the entire length of the cochlea?

A

Scala Media

Cochlear Duct

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15
Q

What separates the scala media from the scala tympani?

A

Basilar membrane

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16
Q

What separates the scala media from the scala vestibuli?

A

Reissner’s Membrane?

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17
Q

How thick is Reissner’s membrane?

A

1-2 cells only

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18
Q

What is the purpose of the stria vascularis?

A

It supplies blood to the organ of corti.

It maintains its metabolic processes and balances

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19
Q

What is the triangular shaped tunnel that gives structure to the organ of corti?

A

The tunnel of corti

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20
Q

Where can cordilymph be found?

A

In the tunnel of corti

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21
Q

How many inner hair cells do humans have?

A

Around 3500

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22
Q

How are inner hair cells arranged?

A

In small bundles of 40-60 stereocillia.

These are arranged in a U-shape

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23
Q

What are the cup-like cells that support the hair cells?

A

Dieter’s cells

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24
Q

What are the cells that press laterally on the inner hair cells to help hold them in place?

A

Cells of Hensen

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25
Q

How many rows of outer hair cells do humans have?

A

3-5

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26
Q

How many stereocilia are on each outer hair cell?

A

150

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27
Q

How are the stereocilia of outer hair cells arranged?

A

In a V or W shape

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28
Q

What happens as a result of the stapes moving the inner ear fluid?

A

A pressure wave is generated in the fluid along the basilar membrane

This deflects as a traveling wave

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29
Q

What is the maximal deflection of the basilar membrane dependent on?

A

The frequency of the input

High frequency sounds produce maximal displacement at the the basal end of the cochlea

Low frequency sounds produce maximal displacement at the the apical end of the cochlea

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30
Q

What happens when the stereocilia are sheared?

5

A

The tip links are tightened (IHC)

This causes the ion channels to open

The causes an influx of potassium ions (K+)

This releases neural transmitters that stimulate the spiral ganglion

This generates an action potential

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31
Q

What is depolarization?

A

Making a cell more positive or negative

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32
Q

Endocochlear Potential

A

The resting potential of endolymph

Approximately 80 mV

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33
Q

What is the intercellular resting potential?

A

-70mV

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34
Q

What is the difference between the resting potential of endolymph and that of hair cells?

A

80 mV + (-70) mV

= 150 mV

This is the highest voltage difference in the entire body

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35
Q

What is responsible of maintaining resting potentials?

A

Stria Vascularis

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36
Q

What happens when there is damage to the stria vascularis?

A

The resting potential difference is reduced and the ear becomes less sensitive

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37
Q

Cochlear Microphonic

A

Only observable when a stimulus is present

Mimics the acoustical input’s frequency and input

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38
Q

What is the magnitude of the cochlear microphonic proportional to?

A

The displacement of the basilar membrane

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39
Q

Action Potential

A

Sum of many individual neurons firing simultaneously

It starts out negative, gradually becomes positive, then becomes negative again.

It reflects the electrical activity of the cochlea

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40
Q

Summating Potential

A

A DC potential that only occurs with acoustic stimulation

Can be positive or negative

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41
Q

What happens because the outer hair cells touch the tectorial membrane?

A

The inner hair cells are more likely to be stimulated by fluid motion

42
Q

Motility

A

The Outer Hair Cells ability to change size

43
Q

How fast does the motility of the outer hair cells change?

A

Very rapidly (tenths of milliseconds)

Very slowly (several seconds)

44
Q

What does the motility of the outer hair cells accomplish?

A

It changes the overall mechanical stiffness of the basilar and tectorial membrane

45
Q

What causes cochlear emissions?

A

The motility of the outer hair cells

46
Q

Otoacoustic Emissions

A

Provide amplification

Narrowband acoustic signals generated by ears that hear normally

Can occur with or without stimulation

47
Q

Spontaneous Emissions

A

Otoacoustic Emissions that occur without a stimulus

48
Q

Evoked Emissions

A

Otoacoustic Emissions that occur with a stimulus

49
Q

What causes most forms of hearing impairment?

A

The weakening or loss of otoacoustic emissions (OAEs)

50
Q

What do we call the cavity in the temporal bone which houses the inner ear?

A

Labyrinth

51
Q

What types of labyrinths are there?

A

Bony Labyrinth

Membranous Labyrinth

52
Q

Where do we get the word labyrinth?

A

From Greek

It means a maze

53
Q

How many turns does the cochlea have?

A

2 1/2

54
Q

What is the “window” part of the oval window and the round window?

A

Skin

55
Q

What is the purpose of the round window?

A

It equalizes the pressure created when the stapes presses the oval window

56
Q

What fills the bony labyrinth?

A

Perilymph

57
Q

What is perilymph similar to?

A

Cerebrospinal Fluid

58
Q

What does perilymph have a similar ionic composition to?

A

Extracellular Fluid

59
Q

Where can you find perilymph?

A

Scala Vestibuli

Scala Tympani

Vestibule

60
Q

What is the membranous labyrinth composed of?

4

A

Semicircular canals

Utricle

Saccule

Scala Media

61
Q

What does Reissner’s Membrane do?

A

Separates the Scala Vestibuli from the Scala Media

62
Q

What does the Spiral Ligament do?

A

Holds the membranes in place

63
Q

What is the function of the Basilar Membrane?

A

Separates the Scala Tympani from the Scala Media

Houses the sensory cells

64
Q

What is the Osseous Spiral Lamina?

A

A thin shelf of bone

65
Q

Where is the Basilar Membrane the widest?

A

At the Apex

66
Q

Where is the Basilar Membrane the stiffest?

A

At the base

67
Q

Where is the basilar membrane the narrowest?

A

The base

68
Q

Where does the basilar membrane have more mass?

A

The apex

69
Q

Where is the basilar membrane less stiff?

A

The apex

70
Q

Where is the basilar membrane the most tense?

A

The base

71
Q

Where is the basilar membrane the most flaccid?

A

The apex

72
Q

How can otoacoustic emissions be measured (OAEs)?

A

By inserting a tiny microphone at the entrance of the ear canal

73
Q

What is a kinocilium?

A

It is the tallest of the stereocilia

74
Q

What happens when the outer hair cells are pushed by the basilar membrane into the tectorial membrane?

A

The stereocilia are pushed into the kinocilium

75
Q

What happens when the basilar membrane pulls away from the tectorial membrane?

A

The stereocilia are bent away from the kinocilium

76
Q

What are the pivot points in the organ of corti?

A

The points where the basilar membrane connects to the spiral lamina and the spiral ligament.

This is where the membrane starts to move

77
Q

Which part of the basilar membrane moves the slowest?

A

The apex

78
Q

Which part of the basilar membrane moves the fastest?

A

The base

79
Q

Which hair cells are damaged or die first?

A

The high frequencies at the base of the cochlea

This is probably due to the scrubbing or shearing motion

…or the continual pounding of the stapes at the oval window for noise induced loss

80
Q

What makes the inner hair cells move back and forth?

A

The movement of the fluid between the basilar and tectorial membranes

81
Q

What is the resting potential of perilymph?

A

0-5 mV

82
Q

What is the resting potential of Endolymph?

A

80 mV

83
Q

What kind of electrical charge do hair cells have?

A

Highly negative

84
Q

Can a malfunctioning stria vascularis cause hearing loss?

A

Yes.

85
Q

What is a good metaphor for the stria vascularis?

A

The battery of the cell

86
Q

What does the stria vascularis do?

A

It pumps charged (+) ions into the hair cells and then pumps them out again

87
Q

For the outer hair cells, current causes ___________.

A

The hair cell to exhibit “motility” or movement

88
Q

How do the outer hair cells move?

A

They lengthen and shorten

89
Q

What allows the outer hair cells to move?

A

The reaction of prestin to potassium

90
Q

For the outer hair cells, motility _________.

A

Generates force

91
Q

How does the outer hair cells’ motility affect the basilar membrane?

A

It increases its displacement

92
Q

For the outer hair cells, the increase of input from the OHC’s motility is called ____________.

A

Cochlear Amplification

93
Q

The cochlear amplifier effect _______ and ________ for _______.

A

Improves the sensitivity

Improves frequency selectivity

The Basilar Membrane

94
Q

When does the basilar membrane exhibit a passive response?

A

When there is hearing loss

95
Q

When does the basilar membrane exhibit an active response?

A

When there is normal hearing

96
Q

Where is fluid pumped from during the up and down motion of the basilar membrane?

A

Internal Spiral Sulcus

97
Q

What are the different ways the sound signal is transduced?

4

A

Mechanically

Hydromechanically

Electrochemically

Electrically

98
Q

How is the sound signal transduced mechanically?

4

A

Tympanic Membrane

Ossicular & Stapes Movement

Traveling Wave

Shearing of the Stereocilia

99
Q

How is the sound signal transduced hydromechanically?

A

Movement of the perilymph within the cochlea

100
Q

How is the sound signal transduced electrochemically?

A

The change in the ionic composition within the hair cell

101
Q

How is the sound signal transduced electrically?

A

Action potential

102
Q

What causes shearing of the stereocilia?

A

The movement of the basilar membrane

Intro to Audiology (11 decks)

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